The detrimental effects of the burning of fossil fuels on the environment are becoming more and more of a concern and have spurred great interest in alternative energy sources. While progress is being made with solar, wind, nuclear, geothermal, and other energy sources, it is quite clear that the widespread availability of economical alternate energy sources, in particular for high energy use applications, remains an elusive target. In the meantime, fossil fuels are forecast to dominate the energy market for the foreseeable future. Among the fossil fuels, natural gas is the cleanest burning and therefore the clear choice for energy production. There is, therefore, a movement afoot to supplement or supplant, as much as possible, other fossil fuels such as coal and petroleum with natural gas as the world becomes more conscious of the environmental repercussions of burning fossil fuels. Unfortunately, much of world's natural gas deposits exist in remote, difficult to access regions of the planet. Terrain and geopolitical factors render it extremely difficult to reliably and economically extract the natural gas from these regions. The use of pipelines and overland transport has been evaluated, in some instances attempted, and found to be uneconomical. Interestingly, a large portion of the earth's remote natural gas reserves is located in relatively close proximity to the oceans and other bodies of water having ready access to the oceans. Thus, marine transport of natural gas from the remote locations would appear to be an obvious solution. The problem with marine transport of natural gas lies largely in the economics. Ocean-going vessels can carry just so much laden weight and the cost of shipping by sea reflects this fact, the cost being calculated on the total weight being shipped, that is, the weight of the product plus the weight of the container vessel in which the product is being shipped. If the net weight of the product is low compared to the tare weight of the shipping container, the cost of shipping per unit mass of product becomes prohibitive. This is particularly true of the transport of compressed fluids, which conventionally are transported in steel cylinders that are extremely heavy compared to weight of contained fluid. This problem has been ameliorated somewhat by the advent of Type III and Type IV pressure vessels. Type III pressure vessels are comprised of a relatively thin metal liner that is wound with a filamentous composite wrap, which results in a vessel with the strength of a steel vessel at a substantial saving in overall vessel weight. Type IV pressure vessels comprise a polymeric liner that is likewise wrapped with a composite filamentous material. Type IV pressure vessels are the lightest of all the presently approved pressure vessels. The use of Type III and Type IV vessels coupled with the trend to make these vessels very large—cylindrical vessels 18 meters in length and 2.5-3.0 meters in diameter are currently being fabricated and vessel 30 or more meters in length and 6 or more meters in diameter are contemplated—has resulted in a major step forward in optimizing the economics of ocean transport of compressed fluids.
All pressure vessels require at least one end fitting, called a “boss,” for connecting the vessel to external paraphernalia for loading and unloading fluids into and out of the vessel. Bosses in current use are generally made of metals such as stainless steel, nickel alloys, aluminum, brass and the like. Unfortunately, bosses, in particular with regard to larger pressure vessels, are extremely heavy, by some estimates comprising as much as 70% of the weight of a Type III or Type IV pressure vessel. Further, large metal bosses are difficult to manufacture and tend to be expensive, often costing $100,000 or more. These factors have a huge negative effect on the economics, and thereby the viability, of ocean transport of compressed fluids. A polymeric composite boss would substantially lighten any of the classes of vessels, in particular Type III and Type IV vessels.
In copending patent application Ser. No. 14/362,477, which is incorporated by reference as if fully set forth herein, such composite boss is disclosed.
A presently preferred filler for use in the composite from which the above boss may be fabricated is fibrous or filamentous carbon. Since composites with fibrous carbon filler are electrically conductive, i.e., have an electrical potential, a problem may arise due to galvanic corrosion if the composite comes in contact with a substance having a different electrical potential, particularly in the presence of a conductive atmosphere such as would be found in salt-laden moist sea air encountered during marine transport.
Thus, what is needed is a method of preventing carbon fiber or filament composite bosses from participating in galvanic corrosion. This application is directed to such a method.